Program - Brookhaven National Laboratory

The A = 130 Solar-System r-process Abundance Peak - from Initial Build-Up to Decay
Back to β-stability
K. Farouqi, K.-L. Kratz
Mainz University
P. Möller
Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
W.B. Walters
University of Maryland
Since the seminal work of Burbidge et al., Cameron, and Coryell more than 50 years ago, the ability to
correctly reproduce the total Solar-System (SS) isotopic r-process abundance pattern has served as a key
test for the nuclear-physics data input far from b-stability, and nucleosynthesis models. In this context,
the A = 130 abundance peak is of particular importance because, on the one hand, its formation is directly
related to the N = 82 shell closure below doubly-magic Sn-132 and, on the other hand, represents the
major bottle neck for the r-process matter flow to heavier elements up to the A = 195 abundance peak and
the actinide r-chronometers. The quality and usefulness of such calculations have been aided over the past
20 years by the use of (i) improved r-process models, (ii) a consistent theoretical nuclear-physics input, and
(iii) the inclusion of experimental nuclear data of (today) about 80 isotopes between Fe and Te that directly
lie in the r-process ”boulevard”. As object examples, using the theoretical nuclear-physics input based on
the older mass formula ETFSI-Q, as well as new mass model FRDM 2012 [1], we present new parameterized
nucleosynthesis calculations of an r-process in high-entropy-winds of core-collapse supernovae. For different
choices of correlated astrophysical parameters for medium-temperature, hot and cold r-process conditions,
we study in detail the formation of the A = 130 abundance peak and follow the modulation of its initial
shape during the complete freezeout and beta-decay back to stability. We will present time-scales for
reaching the first stable isotopes, such as 124Sn, 130Te and 136Xe. In this context, we will emphasize
the importance of beta-delayed neutron emission and its late recapture, in some cases leading to minor
production of historical ”s-only” isotopes.
Corresponding author: W.B. Walters
[1] P. Möller & K.-L. Kratz, to be submitted to ADNDT
LB 5 5:00 PM
Measurement of the Thulium Stellar Cross Section at kT=30 keV by Activation with an
Innovative Method
J. Praena, Departamento de Fìsica Atómica, Molecular y Nuclear, Universidad de Sevilla, Spain.. M.
Pignatari, Basel University, Switzerland. P. F. Mastinu, Laboratori Nazionali di Legnaro, INFN, Padova,
Italy. J. M. Quesada, Departamento de Fìsica Atómica, Molecular y Nuclear, Universidad de Sevilla,
Spain.. R. Capote, International Atomic Energy Agency, NAPC-Nuclear Data Section.
The production of Maxwell-Boltzmann neutron spectra is of interest in several fields. Maxwellian-averaged
cross sections (MACS) ranging from kT=5 keV to 120 keV are key parameters in the calculation of the
astrophysical reaction rates of nucleon, photon and charged-particle interactions with the different elements
and their isotopes needed among other things for the description of observed elemental abundances.
Spectrum average (SPA) cross sections measured in the well-characterized maxwellian neutron spectrum
with high accuracy could be used for the validation of nuclear data libraries in the above-mentioned energy
range. Both the library cross-section value and corresponding covariances could be challenged. The
estimated uncertainty from the nuclear data library of SPA cross sections is directly linked to off-diagonal
elements of the uncertainty matrix; therefore the uncertainty of the calculated SPA cross-section is sensitive
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